# ­xkcd thread **URL:** \ **Category:** Cafe Society\ **Tags:** comic-strips\ **Created:** [May 28, 2020, 12:57am UTC](https://boards.straightdope.com/t/xkcd-thread/854574 "2020-05-28T00:57:03Z")\ **Posts on this page:** 20\ **Page:** 233
**Author:** ![Ponderoid](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ponderoid/32/19221_2.png) [@Ponderoid](https://boards.straightdope.com/u/Ponderoid)\ **Post date:** [July 10, 2025, 1:57am UTC](https://boards.straightdope.com/t/xkcd-thread/854574/4643 "2025-07-10T01:57:47Z")
That nuclear engineer who reacts to all of the _What If_ episodes on youtube thought of something else nobody here has brought up: a [Black Hole Moon would stop slowing the Earth’s rotation](https://youtu.be/Y7MdF1F9-xY?t=138). ---
**Author:** ![Lumpy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lumpy/32/446_2.png) [@Lumpy](https://boards.straightdope.com/u/Lumpy)\ **Post date:** [July 10, 2025, 2:07am UTC](https://boards.straightdope.com/t/xkcd-thread/854574/4644 "2025-07-10T02:07:39Z")
I’m not sure that’s correct; I thought the primary mechanism was the moon’s drag on a tidally distorted Earth. ---
**Author:** ![Dr.Strangelove](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dr.strangelove/32/6613_2.png) [@Dr.Strangelove](https://boards.straightdope.com/u/Dr.Strangelove)\ **Post date:** [July 10, 2025, 2:29am UTC](https://boards.straightdope.com/t/xkcd-thread/854574/4645 "2025-07-10T02:29:03Z")
Yeah; Earth’s distortion of the Moon is what caused it to present only one face to us, while the Moon’s distortion of Earth is what’s slowing the day. And both of them together contributed to the Moon moving farther away over time, though the Moon is no longer contributing today. ---
**Author:** ![Northern\_Piper](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/northern_piper/32/5304_2.png) [@Northern\_Piper](https://boards.straightdope.com/u/Northern_Piper)\ **Post date:** [July 10, 2025, 2:33am UTC](https://boards.straightdope.com/t/xkcd-thread/854574/4646 "2025-07-10T02:33:40Z")
What was the biggest the moon ever looked from Earth? (Setting aside there wouldn’t have been anyone to see it.) ---
**Author:** ![Dr.Strangelove](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dr.strangelove/32/6613_2.png) [@Dr.Strangelove](https://boards.straightdope.com/u/Dr.Strangelove)\ **Post date:** [July 10, 2025, 2:39am UTC](https://boards.straightdope.com/t/xkcd-thread/854574/4647 "2025-07-10T02:39:40Z")
It would have been an incandescent blob that covered the entire sky (moments after the colliding object that created the Moon impacted). Once it coalesced into something vaguely spherical? No one is quite sure about that, but probably a few degrees across (compared to the current 0.5 degrees). ---
**Author:** ![Dr.Strangelove](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dr.strangelove/32/6613_2.png) [@Dr.Strangelove](https://boards.straightdope.com/u/Dr.Strangelove)\ **Post date:** [July 10, 2025, 2:47am UTC](https://boards.straightdope.com/t/xkcd-thread/854574/4648 "2025-07-10T02:47:09Z")
Judge for yourself: [![](https://img.youtube.com/vi/kRlhlCWplqk/maxresdefault.jpg "New Supercomputer Simulation Sheds Light on Moon’s Origin") ](https://www.youtube.com/watch?v=kRlhlCWplqk) It’s all highly speculative, of course. A large impactor is the best theory we have of the Moon’s formation, but it’s impossible to know the details. Just possible scenarios. ---
**Author:** ![Northern\_Piper](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/northern_piper/32/5304_2.png) [@Northern\_Piper](https://boards.straightdope.com/u/Northern_Piper)\ **Post date:** [July 10, 2025, 2:54am UTC](https://boards.straightdope.com/t/xkcd-thread/854574/4649 "2025-07-10T02:54:41Z")
Thanks for that. Interesting. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [July 10, 2025, 1:08pm UTC](https://boards.straightdope.com/t/xkcd-thread/854574/4650 "2025-07-10T13:08:23Z")
I think that any science resulting from observations of total solar eclipses would rely on the same person seeing multiple ones. Your first solar eclipse, you’re too caught up in the “Ooh, wow” to be able to do much, and even if you do observe something, there’s too much of the “What the Hell did I just see? Did I actually see it?” factor. And one person seeing multiple eclipses relies on both being able to predict them very precisely, and on a person having the wherewithal to travel to the right places. Both of which were difficult, until very recently. ---
**Author:** ![Pleonast](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/pleonast/32/1183_2.png) [@Pleonast](https://boards.straightdope.com/u/Pleonast)\ **Post date:** [July 10, 2025, 1:57pm UTC](https://boards.straightdope.com/t/xkcd-thread/854574/4651 "2025-07-10T13:57:33Z")
> [@Chronos](#): > > > [@Dr.Strangelove](#): > > > > Newton would have figured out gravity anyway; the biggest motivating factor was figuring out the laws of planetary motion, which wouldn’t be affected. > > But the biggest clue was that an inverse-square law would account for both surface gravity and the Moon’s orbit. Copernicus, Brahe, and Kepler had already laid the groundwork for an inverse-square law for planetary motion. Their work would still have been done without a visible moon. Perhaps Newton wouldn’t have come up with a law of gravity, but a law of heavenly motion. But I think someone doing artillery tables (taking into account the curvature and rotation of the Earth) would’ve used an inverse-square law even without the astrophysics. I think the Moon is what connects the two areas, but both areas would’ve been using an inverse-square law independently. ---
**Author:** ![Pleonast](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/pleonast/32/1183_2.png) [@Pleonast](https://boards.straightdope.com/u/Pleonast)\ **Post date:** [July 10, 2025, 2:02pm UTC](https://boards.straightdope.com/t/xkcd-thread/854574/4652 "2025-07-10T14:02:28Z")
He missed getting the weights wrong. Having one semi-bold character among bold characters is extremely aggravating. Pick your weight and stick to it. There needs to be another sign with bad color choices. ---
**Author:** ![Andy\_L](https://avatars.discourse-cdn.com/v4/letter/a/c67d28/32.png) [@Andy\_L](https://boards.straightdope.com/u/Andy_L)\ **Post date:** [July 10, 2025, 2:43pm UTC](https://boards.straightdope.com/t/xkcd-thread/854574/4653 "2025-07-10T14:43:28Z")
So the slowdown would continue at a rate very close to that which occurs today ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [July 10, 2025, 3:07pm UTC](https://boards.straightdope.com/t/xkcd-thread/854574/4654 "2025-07-10T15:07:52Z")
> [@Pleonast](#): > > But I think someone doing artillery tables (taking into account the curvature and rotation of the Earth) would’ve used an inverse-square law even without the astrophysics. You need awfully powerful artillery before you start needing to use an inverse-square law for gravity. It’d probably show up for something like battleship guns, or the rail artillery of WWII, but that’s a long time after Newton. And in many ways, what was biggest about Newton’s law of gravity was that it was universal. It’s easy to say that there must be some laws that govern the motions of the heavens, and with enough time and effort, those laws would have been determined. But what was significant, to the history of science, was that the laws of the heavens are the same as the laws of the Earth. Without observations of an object orbiting the Earth, preferably at far above LEO, that crucial connection would have been nearly impossible. > [@Pleonast](#): > > He missed getting the weights wrong. Having one semi-bold character among bold characters is extremely aggravating. Pick your weight and stick to it. Which character are you seeing as semi-bold? They all look the same to me. (of course, once pointed out, I probably won’t be able to unsee it) ---
**Author:** ![EllisDee](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ellisdee/32/4531_2.png) [@EllisDee](https://boards.straightdope.com/u/EllisDee)\ **Post date:** [July 10, 2025, 3:36pm UTC](https://boards.straightdope.com/t/xkcd-thread/854574/4655 "2025-07-10T15:36:57Z")
> [@Chronos](#): > > Which character are you seeing as semi-bold? They all look the same to me. None. They’re saying one of them should be. ---
**Author:** ![Pardel-Lux](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/pardel-lux/32/20182_2.png) [@Pardel-Lux](https://boards.straightdope.com/u/Pardel-Lux)\ **Post date:** [July 10, 2025, 3:37pm UTC](https://boards.straightdope.com/t/xkcd-thread/854574/4656 "2025-07-10T15:37:54Z")
> [@Chronos](#): > > Without observations of an object orbiting the Earth, preferably at far above LEO, that crucial connection would have been nearly impossible. My argument precisely. And if you have an invisible moon mass up there messing up the data figuring out the universality of the law is even more difficult. You will always be fighting a counterexample, and a big one, not a trivial one. **Dr.Strangelove** argues from his vantage point, already knowing the solution. Assuming this hypothetical invisible moon I would not be surprised if the ancient scientists were out-argued by religious types who would say that the laws of motion and gravity apply to the far realms, like the Jovian Moons, and to the Sun and the planets, but not to Earth, because Earth is special. God made it for us. Our place in the Universe is singular. Far fetched? Hell, some people still argue like that! ---
**Author:** ![Dr.Strangelove](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dr.strangelove/32/6613_2.png) [@Dr.Strangelove](https://boards.straightdope.com/u/Dr.Strangelove)\ **Post date:** [July 10, 2025, 10:35pm UTC](https://boards.straightdope.com/t/xkcd-thread/854574/4657 "2025-07-10T22:35:38Z")
People argue all sorts of things. Eventually, experiment proves them right or wrong. The Schiehallion experiment determined that gravity works locally and that it follows inverse square (also estimating the density of Earth). > **[Schiehallion experiment](https://en.wikipedia.org/wiki/Schiehallion_experiment)** > > .mw-parser-output .geo-default,.mw-parser-output .geo-dms,.mw-parser-output .geo-dec{display:inline}.mw-parser-output .geo-nondefault,.mw-parser-output .geo-multi-punct,.mw-parser-output .geo-inline-hidden{display:none}.mw-parser-output .longitude,.mw-parser-output .latitude{white-space:nowrap}56°40′4″N 4°5′52″W / 56.66778°N 4.09778°W / 56.66778; -4.09778 > The Schiehallion experiment was an 18th-century experiment to determine the mean density of the Earth. Funded by a grant from the Royal So... ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [July 10, 2025, 10:59pm UTC](https://boards.straightdope.com/t/xkcd-thread/854574/4658 "2025-07-10T22:59:00Z")
Sure, if anyone did that experiment. And eventually, someone would have. But it would have taken a lot longer. ---
**Author:** ![Dr.Strangelove](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dr.strangelove/32/6613_2.png) [@Dr.Strangelove](https://boards.straightdope.com/u/Dr.Strangelove)\ **Post date:** [July 10, 2025, 11:02pm UTC](https://boards.straightdope.com/t/xkcd-thread/854574/4659 "2025-07-10T23:02:57Z")
I dunno. Maybe it would have been done earlier. Without the Moon to demonstrate gravity for nearby objects, there would be _increased_ motivation for a local experiment. Plus, the Moon only gives a single extra data point, whereas with a mountain you can go to multiple distances and show that they match the curve. ---
**Author:** ![LSLGuy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lslguy/32/5813_2.png) [@LSLGuy](https://boards.straightdope.com/u/LSLGuy)\ **Post date:** [July 11, 2025, 3:12pm UTC](https://boards.straightdope.com/t/xkcd-thread/854574/4660 "2025-07-11T15:12:13Z")
> [@Dr.Strangelove](#): > > Judge for yourself: Darn convenient for us that the impact was that far off-center. Much closer to center-to-center and the Earth may have ceased to be a coherent body forever. Instead just smeared out into a mini asteroid belt. ---
**Author:** ![dtilque](https://avatars.discourse-cdn.com/v4/letter/d/d6d6ee/32.png) [@dtilque](https://boards.straightdope.com/u/dtilque)\ **Post date:** [July 11, 2025, 5:17pm UTC](https://boards.straightdope.com/t/xkcd-thread/854574/4661 "2025-07-11T17:17:06Z")
> **[Building a Fire](https://xkcd.com/3114/)** [![](https://imgs.xkcd.com/comics/building_a_fire.png) ](https://imgs.xkcd.com/comics/building_a_fire.png) “That was quicker than usual! The cabin’s sprinkler system often makes it really hard to keep anything lit.” ---
**Author:** ![Lumpy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lumpy/32/446_2.png) [@Lumpy](https://boards.straightdope.com/u/Lumpy)\ **Post date:** [July 11, 2025, 5:26pm UTC](https://boards.straightdope.com/t/xkcd-thread/854574/4662 "2025-07-11T17:26:46Z")
FWIW, the campfire guides I’ve read (and personal experience) suggest that the “pigsty” configuration of a wall of fuel surrounding a core of tinder isn’t a very efficient method. [Previous page](https://boards.straightdope.com/t/xkcd-thread/854574.md?page=232) [Next page](https://boards.straightdope.com/t/xkcd-thread/854574.md?page=234)